Fans of MI, do not worry! This game is just as good as the first 3 Monkey Islands, and better than MI4!
But do not fear! Monkey Island Ep1 is awesome!
Graphics - Once you get used to them, they suit the series really well. Sure, they're not curse, but it's easily got the number 2 position for best MI graphics. Guybrush looks great, the buildings look great and menus are freaking awesome.
Sound - Really good. A lot of the songs are MI remixes, so you will instantly recognize a good number of the songs. Up to Monkey Island standards.
Humour - Great. Theres some really funny bits in there and it even references Wallace and Gromit at one point (one of telltales other games).
Puzzles - Challenging at times, but it's normally pretty easy. You'll most likely spend 20min of your 3-4 hours being stuck, which I thought was really good. The hint system also helps, and theres the option to turn this off if you want. They're definitely up to the MI standard.
If you like Monkey Island, GO BUY THIS GAME. You won't be disappointed.
(it even has Chuck the Plant in it!)